Run all of a group of shell-based tests, despite any failures
"make repotool-regress" and friends (i.e. the targets that loop in test/Makefile over a bunch of $NAME.sh tests) bail out on the first test failure. This change makes each such target run all of its tests, while still exiting with an appropriate status.
[ The corresponding "-buildregress" targets have not been changed; for those, failing fast seems arguably more useful than in the "-regress" case. ]